There are two main lines of work in this grant: 1) to further work out the wiring diagram of the simple nervous system of the leech and 2) to pursue our study of the ventral root afferents. In the leech we will study the nature of the inhibitory transmitter of cell 119. In the central root, we will attempt to follow the central processes of the ventral root afferents by injecting radioactive amino acids into the dorsal root ganglion and follow the processes of the ganglion cells centrally. BIBLIOGRAPHIC REFERENCES: McAdoo, David J. and R.E. Coggeshall. 1976. Gas Chromatographic-mass spectrometric analysis of biogenic amines in identified neurons and tissues of Hirudo medicinalis, J. Neurochemistry, 26: 163-167. Sawada, M. and R.E. Coggeshall. 1976. Ionic mechanism of 5-hydroxtryptamine induced hyperpolarization and inhibitory junctional potential in body wall muscle cells Hirudo medicinals. J. Neurobiology, 7: 63-73.